Month: January 2020

Geen categorie Lens tests Nikon

Focus breathing and more

On, I got the request to answer this question:

Adam Palmer and 1 other person are looking for an answer to:
Why does the 70mm end of my Sigma 70-200 F2.8 looks so much more zoomed in than the 70mm end of my Sigma 24-70 F2.8? They’re both full frame lenses being used in my Nikon D7500 APS-C.

Here’s my answer:
Focus breathing plus accepted tolerance. The focal length is defined when focused at infinity. Yet all lenses with internal focusing change their focal length while focusing. (Zoom lens are almost always internal focusing, otherwise, they would need an enormous helicoid and get very large.) You have to imagine a zoom lens has a moving group lens elements for zooming, another moving group of lens elements for focusing and yet another moving group of lens elements to compensate for the focus changes while zooming (so to keep it sharp while zooming). I don’t know if you ever had two girlfriends or whatever at the same time (or whether your girlfriend or whatever had two you’s at the same time), but you can imagine that it makes things complicated. Same in a zoom lens.

In short: This means that the focal length gets shorter when getting closer. In the case of a 70mm that might mean it’s effectively 65 or even 60mm up close. It’s mostly not a big deal, it’s just one of the many consequences of lens design, which is one big tradeoff. Now I don’t know which Sigmas you are referring to, but the 24-70mm f/2.8 ART suffers from some focus breathing at the long end. Several iterations of Sigma’s 70-200mm f/2.8 too as far as I remember, and then also on the long end. So if you set both lenses to 70 mm, one will suffer from focus breathing a lot more than the other, since in one case 70mm is the short end, in the other, it’s the long end.

Another fact of life is that focal lengths do have some tolerances. 70 mm even at infinity, is never exactly 70 mm. It will more likely to be something like 67,6 mm or 72,4 mm. If your lens suffers from focus breathing, this is one of the ways to compensate for it, but sometimes it’s just the way a lens design turns out. There are also ISO tolerances here, so don’t start to measure your lens and hope to get your money back. And really, those are general things, all manufacturers basically have to deal with the same optical limitations in lens designs and then make their own tradeoffs.

If you own the Sigma Art, you will probably also notice the 24-70 is less sharp in the corners at 70mm. So keep that in mind and change to the 70-200mm while making pictures if you need the focal length and/or sharpness.

One last remark: the fact that you use a D7500, so an APS-C camera with those lenses, doesn’t change anything, as long as you use the same camera with both lenses. The camera crops the image 1.5 x but in both cases.

Canon Lens review Lens tests Nikon

New 70-200-zooms from Nikon and Canon and a superior 120-300mm f/2.8

Canon and Nikon are churning out new lenses for their mirrorless camera quickly now. All lenses for the new mounts have proven to be excellent, no surprises so far. Now we finally see the introduction of the respective 70-200mm f/2.8s. These lenses are very interesting because they are the most difficult to develop – in decent quality, that is. Telezooms have originally been a specialty for Nikon. The 80-200mm f/4.5 was the first zoom lens that was as good as primes, ‘the zoom that ends all other zooms’. The 85-250mm f/4-4.5 (1959) was even the first tele zoom lens in the world. By the time Nikon introduced the first 80-200mm f/2.8 Canon joined Nikon and has been able to offer the same quality.

But when Nikon introduced the 70-200mm f/2.8 FL, the third generation of 70-200mm f/2.8s, Canon didn’t really follow. They just reintroduced the second generation and changed the coating somewhat. So Nikon’s 70-200mm became the best 70-200mm you could buy.

Now we see both brands introducing a 70-200mm f/2.8 for mirrorless. And for the first time, we see a completely different approach. Canon designed a lens that used a feature we saw only in amateur lenses so far, a lens with an extending barrel. This construction was considered unfit for pro lenses, since if you bump against something with the lens, it might get misaligned because the barrel or the cams get damaged.

But apparently Canon gave this construction a real good thought and was able to make it quite sturdy. Lens Rentals writes: ‘The Canon RF 70-200mm has about the most robust extending barrel mechanism I’ve ever seen. There aren’t the usual three cams sliding about to move this barrel, there are three pairs of them, and each is very large and robust.’ When collapsed, the lens is also less than  2/3 of previous and comparable lenses and the new Nikon: 1070 g and 146 mm vs. 1440 g and 220 mm.

But of course, weight and size are only two parameters. The most important one is the optical quality and the second most important one is the price. Price-wise both lenses are in the same region as their precessors, the Canon a little more expensive, the Nikon even a little less. As for the optical quality: I wasn’t able to test either lens yet, but we do have the MTFs already. Manufacturer MTF’s can’t be compared directly, but in this case, we can find a way around this conundrum. We do have the MTFs of the previous version of the lenses of both Nikon and Canon and I have my own test results of those lenses. If you combine them, you can say a lot of those lenses, assuming that Canon and Nikon didn’t change the way they calculate MTFs in the last year.

So based on that the conclusion will be that both manufacturers did a great job – but a different job. Canon concentrated on making the smallest and lightest 70-200mm f/2.8 on the market, even with stabilization. Based on the MTF, the optical quality will be better than the previous one; somewhat – but not much – less than the previous Nikon 70-200mm f/2.8, the FL version.

Nikon did something completely different. Their 70-200 f/2.8 is almost exactly the same size and weight as the previous one and has stabilization too. So it should be better than that one, but… that lens already was the best in the market and is not even four years old. As unlikely as it may seem, Nikon succeeded in developing a lens that is a whole class above the previous 70-200. The MTF at 200mm looks better than the one of the 180mm f/2.8 prime, and at least equal to the MTFs of both 300mms f/4s, both of which are known to be very good lenses. Based on the MTF one would expect the Nikkor Z 70-200mm f/2.8 S to be the first 70-200mm that also delivers excellent results with converters. That would make the lens even more attractive.

On the other hand, you can’t use the F-converters on this lens. If a hypothetical Z-converter uses the same built principle as the Sony one, it will be very asymmetrical which isn’t good. So we’ll have to wait and see. There are not even converters on the Z roadmap yet. But then again Nikon also introduced a 120-300mm f/2.8 in the F mount. Of course, you can use that lens without any penalty on the Z cameras as well. The MTF at 300mm looks superior, better than the 300mm f/4s and at the level of the 300mm f/2.8 and 400mm f/2.8. So this lens will very likely be an excellent 160-420mm f/4, 185-510mm f/4,8 and a 200-600mm f/5.6 as well. It’s not cheap though. But there’s also a 200-600mm Z lens on the road map. It looks like Nikon owners soon have too many excellent lenses to choose from.

As for Canon: really nice to see a lens a compact and light 70-200mm f/2.8 of high quality. In the last couple of years, we’re seeing more and more lenses that only 10 years ago would have sounded like science fiction. Great times to be a photographer!


Happy 2020 with many great pictures!

I started 2020 the right way: by taking my camera with me and looking for the right spot for my pictures.

A few technical notes: the standard way to make firework pictures is to choose a very long exposure or even B or T. However, this will often lead to overexposed pictures. Making several exposures and combining them in Photoshop layers is a better solution. You should be careful anyway because not all firework has the same exposure and even things like fog have an influence on exposure. So it’s always a bit of trial & error. As a rule, you should use noise reduction for long exposures. In this case, I chose not to use it, because I was afraid I’d miss too many moments. I ended up making the shadows darker anyway, so there was no noise in the image. If you have camera with a smallish or less good sensor, NR in Photoshop might be a good solution.

For the blending mode of the layers, you might want to use lighten, or even hard light. Here I used mostly lighten but with one layer I used blending mode difference to get some extra colors.

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